wadsworth



. J. M. WADSWORTH METHOD AND APPARATUS Foa GRAGKING AND RECTIFYING PETROLEUM oILs AND' THE LIKE original Filed March Al2. 1926 Re. 17,831

ct. 14, l1930.

kresorting to artificial cooling,

Reissued ocr. 14, v193e UNITED ,STATES WADSWOBTH, OF TULSA, OKLAHOMA, ASSIGNOR TO UNIVERSAL OIL PROD- PATENT OFFICE UCTS COMPANY, 0F CHICAGO, ILLINOIS, A CORPORATION 0F SOUTH. DAKOTA METHOD AND APPARATUS FOR CRACKING AND REGTIFYING PETROLEUM OILS AND THE LIKE Original No. 1,692,476, dated November 20, 1928, Serial No. 94,288, led March 12,

for reissue iiled April 2, 1930. Serial No. 441,157.

This invention relates to a novel method and-apparatus for cracking and rectifying petroleum oils and the like.

The majority of stills employed for cracking high boiling point hydrocarbons into low boiling point hydrocarbons now operate with the heating element and reaction chamber under considerable pressure. In`many of the processes, it is the ract-ice :to relieve this pressure down to a out three atmospheres and condenseand rectify the products under this low pressure, which results in rendering rectification exceedingly difficult and necessitates anauxiliary gasoline plant of the absorption or compressor type to recover the gasoline carried away in 'the uncondensed gases relieved from the system. The gasoline made in the system under this low pressure is an unstable product due to its content of dissolved uncondensible gases. LIt is impossible to properly rectify the vapor from such a process under this low pressure without at the top of the 'rectifying column. Processes. in use which do not reduce the pressure beforecondensing make no eiiort to utilize this pressure to rectifylthe vapor and separate its gasoline content from the uncondensible gas.

Anyv hydrocarbon liquid at a given temperature exerts acertain vapor pressure. As this temperature is increased, the'vapor pressure increases until it is suiicient to overcome the pressure above the liquid, when boiling will occur and the more volatile fractions be driven oif.

The primary object of my invention is to utilize the existent pressure of the'system to accomplish rectification of the lighter hydrocarbon components produced in cracking, such as the separation of pressure still gasoline from the so-called non-condensible gases.7^

In this cracking operation, my method is instance,

based upon the fact that the problem involved is one of properly separating four components ofla hydrocarbon mixture, for 1, residual flux; 2, recycle stock; 3, cracked gasoline; and 4, uncondensed gases. So far as I am aware, none of the present tube and tank cracking stills or shell stills recognize the existence of the fourth compo- 1926. Application nent or provide rectifying means for separating the third and fourth components. For this reason the cracked gasoline produced by them contains a considerable amount of these uncondensed gases in dissolved form, and as a result, excessive losses are experienced in handling the commodity. In addition the uncondensed gases leaving the cracked gasoline condenser in most plants, contain av veryconsiderable proportion of gasoline which can only be recovered through an efficient absorption or compression plant. My improved method utilizes the pressure already vexistent and available to accomplish the desired fractionation and yresults in a very marked saving yover present means, and produces increased yields.

Referring again to the prior art, stated that in the operation of any tube or tank pressure system now commercially used, the method pursuedgis to operate these plants under considerable pressure, and temperature for the purpose of destroying the molecular arrangements of the hydrocarbons to effect new groupings, so as to change a portion of the charged stock into hydrocarbons of lower boiling point. Having produced 1 these .lower boilin point hydrocarbons, it is desirable to recti them into their respective components, and as before stated, in doing this I utilize the pressure and temperature already existent in the cracking plant tofconduct the rectification of the lower boiling point hydrocarbons Aformed during cracking, and I carry out this rectiiication under said pressure or ata reduced pressure and `temperature from that existing in the cracking unit. If the pressure and temperature employed during the cracking is not used for rectification, the products cannot be completely obtained without resorting to artificial .cooling at the head of the rectifying column.

Each component of any hydrocarbon series has a. certain vapor pressure for any given temperature and belowr a certain critical temperature and pressure exists in the liquid phase; above this critical temperature and pressure it will exist only in the vapor phase. It is desirable then to conduct the recitification at a temperature and pressure such that the desirable components will exist in the vapor phase.

From the foregoing, it will be understood that the main object of the present invention isto utilize the vapor pressure set up by the liquid resulting from the cracking operation to accomplish sharp rectification of the components of the liquid.A

While I have set forth some of the objects of the present invention, other objects will appear as this description proceeds, and in reading the presen-t description, reference should be had to the accompanying drawing.

The drawing is a diagrammatic view of an apparatus which I have devised for carrying out the improved process.

' The oil to `be subjected to cracking, enters the system by way of the pipe l, and is forced by a pump 2, -through a pipe 3, and a heat exchanger 4, the latter being heated by the vapors leaving a fractionation tower 5, through a pipe 6. The oil after passing through the heat exchanger, flows through a pipe 7 and thenV through a second heat exchanger 8, the latter being heated by the residuum discharged from the column 5, through a pipe 9. The oil thus preheated flowsthrough pi e 10 into a high pressure -pump 11 which orces the same under considerable pressure through a cracking coil 12, where it is heated to a cracking temperature. The heating coil discharges the oil into a reaction chamber 13 of the ordinary type. A suitable pressure regulating valve 14 is attached to the outlet pipe 15 of the reaction chamber, so that vapor and oil can be released from said chamber at any lower pressure desired` This mixture of vapor and oil enters the stripping column 5 about midway between the top and bottom of the same,

and the residuum leaves at the bottom through the pipe 9 andenters the heat exchanger 8, where it functions to preheat the charging stock. From the heat exchanger, the residuum fiows through a pi e 16 to storage. In the column 5, the gasolme and other vapors are separated from the residuum, and these vapors pass ofi' through the heat exchanger 4 by way of pipe 6. This heat exchanger may, if desired, function as a refiux condenser, so that condensate resulting from the vapors may be returned to the top of the column 5 to cool the top of the column and provide the necessary reflux liquid for rectification. Vapors passing through the` heat exchanger 4 are conducted by a pi e 17 to the central portion of a second rectifying column 18, which is equipped with a reflux condenser 19, to which the lightest vapors flow by way of pipe 20. All condensate is refiuxed from this condenser through pipe 21 into the upper portion of the rectifying. column, while the uncondensed gas passes out through a pressure regulating Valve 22 into a pipe 23. The pressure may be released by permitting the same to operate an expansion engine 24, preferably the prime mover of the process itself, for the purpose of securing the work out of this expansion. Further, the cold created by the expansion of the dry gas may be employed to refrigerate a cooling medium in the cooler 25, and this refrigerating medium may be employed to condense the products yielded rom the process. l

In the first rectifying column 5, above the stripping portion-of the same, a recycle stock may be drawn from one of the lower trays and may be fed through a pipe 26 into a fioat pot 27 which controls the passage of thls recycle stock to a pipe 28 that conveys the same to a coil 29 arrangedin the lower portion of the rectifying column 18. Hence, this recycle stock may be used as a heating medium for the second rectifying column. The coi-l 29 has regulating valves 30 and 31, and a bypass pipe 32 is provided for the purposeof by-passing some of the recycle stock past the coil 29. The by-pass has a control valve 33, and the recycle stock is linally discharged through a pipe 34. The rectified gasoline at the lower portion of the column 18 is utilized to control afloat valve 35,"which regulates the flow of the finished gasoline through the discharge pipe 36. y

A valve 38 in the pipe 9` at the lower portion of the column 5 is provided with a fioat 37,

actuated by the residuum at the bottom of the tower 5.

y In practicing my process, the incomin oil is cracked and the cracked- 'vapors an oil are .fed by the pipe 15 into the tower 5, the upper portionof whichisa rectifier and the lower portion of whichpis a stripping still. In the column 5 ythe cracked vapors will rise while the oil will have a tendency to pass downward. Due to this countercurrent contact of vapors and oil the gasoline and other va ors will be sharpely separated from the resi uum,and these` vapors will finally enter the column 18. As this column has a heating means at its low'el'vend, therewill be a temperature gradient therein and this will resu t in sharp separation of the lighter gases from the gasoline vapors. Consequently all the-components which it is desired to incorporate in the finished gasoline will gather at the bottom of the tower 18, and be discharged through the pipe 36, while the lighter components of the mixture which it is Adesired to eliminate from the gasolinev will be discharged frdm the system by way of pipe 23. As the column 18 has a pressure control valve 22 at its gas outlet and a fioat control valve 35 at its liquid outlet, it is obvious that the column 18 will work .under pressure, and consequently the vapor tension of the material undergoing treatment may be utilized to build up a predetermined pressure within the columns 5 and 18. Therefore, I am enabled by my process and apparatus to utilize the pressure and temperature existent for the cracking operation, to rectify the gasoline without resorting to further compression or extremely low temperatures.

The recycle stock after leaving the reboiler section in the second column may be returned to the suction-of the pump. charging the heating element, by 'any suitable means (not shown). This is the preferable way to opcrate in order to conserve whatever heat remains in the recycle stock.

While I have disclosed a preferred embodiment of the invention, -it is obvious that the details of the method and apparatus may be varied without departing from the, basic ideas which I have outlinedV above and which I will hereinafter claim.

What I claim .and desire to secure by Letters Patent is 1. In a method of treating petroleum oils, Cracking the oil under heat and pressure to produce a mixture of gasoline hydrocarbons, hydrocarbons lighter and heavier than gasoline hydrocarbons, and residuum, rectifying said mixture to sharply separate the gasoline hydrocarbons and lighter hydrocarbons from heavier hydrocarbons and residuum, subsequently rectifying said gasoline h drocarbons and lighter hydrocarbons, an separately withdrawing from the second rectification step, rectified liquid gasoline and uncondensed gases, and utilizing during the rectification steps, the vpressure resulting from the cracking step to effectthe second rectification at super-atmospheric pressure and at temperatures from substantially atmosphcric upwardly.

2. In `a method of treating petroleum oils, cracking the oil under heat and pressure to produce a mixture of gasoline hydrocarbons, hydrocarbons lighter and heavier than, asoline hydrocarbons, and residuum, recti ying said mixture and thus sharply separating the gasoline hydrocarbons and lighter hydrocarbons from heavier hydrocarbons and residuum, subsequently rectifying said gasoline hydrocarbons and lighter hydrocarbons, and separately. withdrawin from the second rectification step, rectifie liquid ,gasoline and uncondensed gases, and utilizing the heat and pressure resulting from the cracking step lduring the rectification steps, to edect both rectifications at superatmospheric press-ure and at temperatures fromysubstantially atvmospheric upwardly.

'3. In a'method of treating petroleum oils,

cracking the loil under heat and ressure to produce a mixture -of gasoline hy rocarbons,

hydrocarbons lighter and heavier tha'l' gasoline hydrocarbons, and residuum, rectifylng said mixturevand thus sharply separating thev gasoline hydrocarbons and lighter hydrocarbons from heavier hydrocarbons and re' s iduum, subsequently rectifyirig said gasoline hydrocarbons and liglhter hydrocarbons alone, and separately wit drawing from the second rectification' step, rectified liquid', gasoline and uncondensed gases, utilizing, g

during the4 rectification steps, the heat and pressure resulting from the cracking step to effect the rectification steps at super-atmospheric pressure and attemperatures from substantially atmospheric upwardly, and passing heavier hydrocarbons from the first rectification step through the second recti-A fication step, and out of contact with the liquid therein to furnish the heat used in the second rectification step.

4. In a method of treating petroleum oils, cracking the oil underheat and. pressure to produce a mixture of gasoline hydrocarbons, hydrocarbonslighter and heavier than gasoline hydrocarbons, and residuum, rectifying said mixture and sharply Separating the gasoline hydrocarbons ,and lighter hydrocarbons from heavier hydrocarbons and residuum, subsequently rectifying said gasoline hydrocarbons and lighter hydrocarbons and separately withdrawing from the second rectifica-tion step, rectified liquid gasoline and uncondensed gases, utilizing during the rectification steps, pressure from the cracking step, to effect the rectification steps at superatmospheric pressure and at temperatures .from substantially atmospheric u wardly,

carbons slightly but not below superatmospheric, re'ctifying said hydrocarbons to sharply separate gasoline hydrocarbons 'and lighter hydrocarbons fromA heavier hydrocarbons and residuum, withdrawing the gasoline hydrocarbons and lighter hydrocarbons from the rectification step in the heated condition resulting from the cracking step, separately withdrawing the residuum from'th'e rectification step, also in the heated condition resulting from the cracking step, utilizing said gasoline hydrocarbons, lighter hydrocarbons and residuum to nreheat charging stock, subsequently rectifying said gasoline hydrocarbons and lighter hydrocarbons under superatmospheric pressure derived from the cracking step, to split the same i/nto Stable gasoline and uncondensed gases, 'separately withdrawing from the'second recti# fication step, rectified liquid gasoline and uncondensed gases, and utilizing heavier hydrocarbons in heated condition from the first f rectification step to furnish the heat employed in the second rectification step. t

' 6. An apparatus for treating hydrocarbon oils, comprising an inlet pipe provided with a plurality of heat exchangers and a plurality of pumps, one of saidA pumps being adapted to raise the pressureof the oil above that of the other pump, a cracking unit connectedto said inlet pipe, a first rectifying column, means for feeding hydrocarbons from the cra-cking unit into an intermediate portion `of said column, means for feeding resduum liquid from the lower portion of said column through one of said heat exchangers, a second rectifying column, means for feeding light hydrocarbons from the top of the first rectifying column, through the other one of said heat exchangers and into an intermediate portion of the second column, a heating elemcnt'arranged in the lower portion of the second column, means for feeding a part of,

the material undergoing treatment from the first column through said heating element, a

4reflux condenser, at the upper `portion of the second column, a' gasoline outlet at the lower portion of the sec'ondcolumn, a dry gas outlet from said reflux condenser, and a pressure regulating valve in the last mentioned column to permit the vapor pressure of the material undergoing treatment to exert suf.

ficient pressure inthe columns-to carry out rectificationy without the use of relatively low temperature cooling mediums.

' 7. In a method oftreating petroleum oils, cracking the oil under heat and pressure to produce a mixture containing gasoline hydrocarbons, hydrocarbons lighter and hydrocarbons heavier than gasoline hydrocarbons, rectifying the mixture to sharply separate the gasoline hydrocarbons and lighter hydrocarbons from the hydrocarbons heavier than gasoline, subsequently rectifying said-- gasoline hydrocarbons and lighter hydrocarbons, and sep the second-recti cation step, rectified liquid asoline and uncondensed gases, and utiliz- 4ing during the rectification steps, the pressure resulting from the cracking step to effect Vthe second rectification at superatmospheric pressure and at temperatures from substantially atmospheric upwardly.

8. In a method of treating petroleum oils, cracking the oil under heat and pressure to produce a mixture containing gasoline hydrocarbons, hydrocarbons lighter and hydroycarbons heavier than gasoline hydrocarbons, rectifying the mixture and thussharply separating the asoline hydrocarbons and lighter hydrocarons' from heavier hydrocarbons, subsequently rectifying said gasoline hydrocarbons and lighter hydrocarbons, and separately withdrawing from the second rectification step, rectified liquid gasoline and uncondensed gases, and'utilizing theheat and pressure resulting from the cracking step arately withdrawing from lighter hydrocarbons 'from heavier hydro-4 carbons, subsequently rectifying Vsaid gasoline hydrocarbons and lighter hydrocarbons alone, and separately withdrawing from the second rectification step, rectified liquid asoline and uncondensed gases, utilizing during the rectification steps, the heat and pressureresulting from the cracking step to effect the rectification steps at superatmoslsubstantially jatmospheric upwardly, and passing .heavier hydrocarbons from the first rectification step through the second rectification step`,5 and -out of contact with the 'i liquid therein to furnish the heat used in the second rectification step.

l10. In a method of treating petroleum oils, cracking the oil under heat land pressure to produce a mixture containing gasoline hydrocarbons, hydrocarbons heavler and hydrocarbons lighter than gasoline hydrocarto effect both bons, rectif ing the constituents of the mix-,

ture and s arply separatin the gasoline hydrocarbons and lighter hy rocarbons lfrom heavier hydrocarbons in the mixture, ,subsequently rectifying said gasoline hydrocarbons and lighter hydrocarbons and se arately withdrawing from the second recti cation step rectified liquid gasoline anduncondensed gases, utilizing, during the rectification steps, pressure from the cracking step, to effect the los rectification steps at superatmospheric pressure and at temperatures from substantially atmospheric upwardly, and utilizingbetween the first and -second rectification` steps, the heat from said gasoline hydrocarbons and lighlfer hydrocarbons to -preheat charging stoc JALIES M. WADSWORTH.

85 pherl-c pressure and at temperatures from 

